Core networks are evolving to packet switched networks and old TDM-type networks are gradually being replaced. However many legacy TDM services still exist. These TDM services may be for trunking links (T1/E1/DS3/SONET/SDH) or for voice services, for example. Circuit Emulation Services (CES) are used to provide TDM services in IP/MPLS networks in order to take advantage of these packet switched networks. A TDM Pseudowire (PW) is established across the packet switched network. TDM frames are received from an access circuit at a router at the edge of the packet switched network through an access port on the router. The router then encapsulates the TDM frames and transmits the encapsulated TDM data as packets to a receiving router over the TDM-FW through the packet switched network. IETF and MEF have multiple standards that define how to encapsulate TDM services into TDM-PWs.
One example of a TDM service is G.711 pulse-code modulated voice services. A codec digitizes analog voice traffic using pulse code modulation (PCM). Voice compression techniques within the codec, using special digital signal processors or voice processors, compress the digital traffic. This compressed voice traffic is then sent as the payload of TDM frames to a router at the edge of the packet switched network. The router encapsulates the TDM frames into packets. The packets are sent over the packet switched network and received at a second router, where the compressed voice data is extracted from the received packets and sent as TDM frames to a TDM service.
Even though the bandwidth of TDM PWs in routers is usually small compared to the bandwidth used by other IP or Ethernet services, there are many instances where network operators have small network links and the TDM PW bandwidth is too high. Examples of small network links are microwave communication links and NxT1 channels in SONET. The compression techniques used within the codec can reduce the amount of data being carried. However there is scope for reducing the bandwidth usage in a TDM-PW carrying voice traffic, or indeed any analog traffic, even more.
There is a need to provide a method and system in which the network operator has more flexibility regarding bandwidth usage in CES.